It is quite common for various parties online to exchange signed documents in signed form (such as contracts for remote work). Would these documents have any power in a court of law? Is it necessary to use the original documents for them to have any legal value?
tl;dr: It depends on what the agreement is about.
The form required for a document varies with the type of agreement or contract. This will depend on jurisdiction and specifics, but general rules are:
- In most jurisdictions, in general a valid contract does not need to be in writing, let alone with a personal signature - it can be entered into verbally, with a handshake, or just implicitly (e.g. taking candles in a church and putting the required amount of money into a box). In these cases, the exact form of the agreement is irrelevant, it only matters that there is one. A written document is helpful as proof, but not required.
- Usually, some types of transactions require a specific form by law - usually important transactions such as the sale of real estate. In that case, the required form can vary - sometimes it is a traditional paper document with an original signature, sometimes it a specific official form must be filled in, sometimes an electronic signature, or even a notarized document. This will depend on the type of transaction.
In practice it is good to be able to prove that a contract exists if there is a dispute. For that reason, it is prudent to use a form that allows a (certain degree of) proof. In that respect, a paper document or a document with an officially recognized electronic signature is better, a scanned document or an email are usually okay, a verbal agreement is likely to be problematic.
- In Germany and the United States, a regular sales contract does not require any specific form. A contract can even be formed non-verbally - this is called an Implied-in-fact contract in Common law, or Schlüssiges Handeln in Germany.
- In Germany, a last will must not only be on paper, but must be written by hand by the testator (Bürgerliches Gesetzbuch, §2247 Eigenhändiges Testament). However, there are exceptions for situation where a written last will is not practical.
- In California, a last will must usually be in writing, and signed by two witnesses (California Probate Code, Sec. 6110).
- In Germany, while regular sales contracts do not require a specific form, contracts for the sale or transfer of real estate must be notarized (Bürgerliches Gesetzbuch §311b, Verträge über Grundstücke, das Vermögen und den Nachlass)
There's a good discussion on "electronic" signatures at Wikipedia.
Electronic signatures have been used for a very long time and the New Hampshire Supreme Court ruled that telegraphs could be used as valid contracts back in 1869.
The article linked above provides links to a large number of international jurisdictions and their electronic signature laws.
In the U.S. an electronic signature is defined as "an electronic sound, or process, attached to or logically associated with a contract or other record and executed or adopted by a person with the intent to sign the record." This includes facsimile transmissions or even morse code.
The Uniform Electronic Transactions Act lays out the definition of electronic signatures in the United States. It has been adopted by 47 states, the District of Columbia, Puerto Rico and the U.S. Virgin Islands.
Just because a state didn't adopt the UETA (Illinois, New York and Washington) doesn't mean they don't accept electronic signatures - it just means they have adopted their own legislation regarding electronic signatures.